The present invention relates to an apparatus for cycling and filtering liquids, and more particularly to systems that filter and recycle liquid cleaning solutions used in continuous flow recycling cleaning devices.
Continuous flow recycling has gained widespread acceptance as an effective technique for cleaning carpets, upholstery, fabric, wall coverings and hard surfaces. According to this technique, a liquid cleaning solution is sprayed toward a surface being cleaned. Simultaneously a vacuum source creates a high velocity airstream that draws the atomized liquid toward the surface and into the material beneath the surface in the case of porous material. Almost immediately the airstream is diverted to draw the liquid upwardly away from the surface, along with soil and other contaminants extracted from the surface and porous material beneath the surface. The rapid and abrupt change in direction promotes efficient recovery of most of the cleaning solution, so that recovered solution may be filtered and recycled to extract further foreign matter.
Continuous flow recycling systems often include a tank of liquid cleaning solution supported on a wheel-mounted base. The base also supports a motor and a pump for circulating the cleaning solution, and a vacuum motor and blower for recovering the solution and returning it to the tank. A cleaning head is coupled to the tank through tubing to transport solution from the tank to the cleaning head and through vacuum hosing to transfer recovered solution and air from the cleaning head back to the tank, where the recovered cleaning solution is filtered and recycled.
Alternatively, the surface cleaning apparatus can be self-contained, with a housing that incorporates the necessary motors and contains the cleaning fluid, with the cleaning tool head being mounted directly to the housing, such as through a pair of pivot arms.
In either case, cleaning effectiveness depends on the ability to continuously recycle and filter the cleaning solution. Any accumulation of soil and other contaminants within the tank, especially along the walls of the filter inside the tank, reduces recycling effectiveness.
Accordingly, continuous flow recycling systems have been equipped with backflush features for creating turbulence along the filter walls, to counteract the accumulation of debris along the filter. For example, U.S. Pat. No. 4,696,075 (Grave) discloses a surface cleaning apparatus in which a relatively small cylindrical filter is contained within a tank of liquid cleaning solution. A pump withdraws filtered liquid from the tank along an outlet line. A bleed line is connected to the outlet line through a bypass valve, for diverting a portion of the liquid back to the tank, into the filter interior. Liquid from the bleed line flows out of the filter, counter to the general flow into the filter caused by the pump. The resulting turbulence reduces the accumulation of contaminants.
An enhanced backflow system is shown in U.S. Pat. No. 5,114,574 (Barry). This system likewise employs a relatively small cylindrical filter within a tank of cleaning liquid solution, withdrawing fluid through a pump and using a bleed line to divert some of the liquid back into the filter. The improvement resides in an insert plug mounted within the filter, for guiding liquid flows along inside and outside surfaces of the filter walls.
While effective in many applications, the above arrangements generate a backwash or counterflow that occurs generally over the entire wall surface area of the filter. The filter must be relatively small. Otherwise, the backflow either lacks sufficient force to prevent the collection of debris, or must be provided with such force as to substantially interfere with the desired primary flow, i.e. into the filter for eventual use at the cleaning head. Regardless of the small filter size and the care with which the backflow force is selected, the backflow provides a continuous resistance to flow of liquids into the filter. Filter wall clearance is maintained at the cost of reduced efficiency, because of an energy dissipating turbulence generally over the entire wall of the filter.
Therefore, it is an object of the present invention to provide a liquid cycling and filtering system with a liquid counterflow for effectively maintaining filter clearance with substantially reduced energy dissipation.
Another object is to provide a liquid circulation and filtering system incorporating a reservoir of the liquid, in which a filter within the reservoir can be substantially larger than such filters in conventional systems, with no reduction in the effectiveness of a counterflow for maintaining filter clearance.
A further object is to provide a surface cleaning system including a conduit for providing a liquid counterflow that maintains filter clearance, with a control means that governs the counterflow while also governing the pressure of the liquid at a cleaning tool head of the system.
Yet another object is to provide a liquid cycling system having a counterspray assembly within a filter submerged in the liquid, with one or more spray orifices of the assembly mounted near the filter walls to provide a counterspray upon the walls, in which each orifice moves relative to the walls as a reaction to the force of the spray.